by Alfonso DamianoSOLAR CELL TECHNOLOGY AND PRODUCT UPDATE
Intersolar Exhibition in Munich
Intersolar showed none of the effects of the impending slashing of the German solar program nor of the finance and banking crisis gripping several key solar enabled countries (Spain, Italy and Greece). Stands were ostentatious – excessively large in some cases – and hand-outs would decimate most companies' marketing budgets. But more of that in later commentaries on commerce and politics.
The exhibition was held in some 15 halls of which 6 were devoted to product/production and 6 to systems and utility issues. Most major players were there (with the notable exception of First Solar) plus an amazing range of Chinese second tier companies with first tier ambitions. True to its political and regional status, Solarworld occupied the prime A1 position, next to the world's biggest solar company, Trina Solar.
These stands matched others in an overabundance of marketing and sales staff. Even Q-Cells and Solon – despite recent filings for bankruptcy protection had strong technical and commercial presence. Conergy's lethargy in the market place was not obvious in the dynamism of their presence. What was truly interesting was the concentration on techno treats – from games halls to Trina's FI mock-up and driving simulator.
This all goes to show that impending bankruptcy does not seem to affect the marketing budget – or is there more to the story?
Technologically, the exhibits were of a uniformly high standard, if sometime boring and the product applications decidedly ugly. The message seems to have got through that silicon solar panels have not been as reliable as assumed (and promised) and that the market demands for real 25 year life (to 80% power) have been adsorbed. Of course this shows that the economics of crystalline silicon based solar power – in the average location- is barely cost competitive, even with FITs and subsidies, otherwise why the demand for such a long warranty. This warranty though is a mix of producer warranty – normally up to 12 years to 90% name-plate capacity followed by an insurance program to take the protection out to 25 years. Not much attention, if any, has been directed to end-of-life issues – such as decommissioning and trashing. Nevertheless, attention has been placed on three key issues:
Hot spots are addressed now by 3 busbars which increase the cost of conductors, but reduce losses, so appear to be cost neutral;
Wafer cracking failures are being addressed by improving quality control in ingot processing and in sawing;
Bubbles in encapsulants have been a significant cause of medium term failure – so major manufacturers now warrant bubble free product.
As a result, there is higher confidence that the modules will survive in the more demanding hot and humid climates into which they are now being sold. Even in China, manufacturers now pride themselves on fully automated manufacturing plants (possibly to the dismay of the US companies that have complained about dumping).
Other areas of development and improvement include conductors (higher conductivity pastes), glass (thinner and tougher), EVA equivalents for backsheets and cover sheets that cure more quickly and have special properties such as thermal conductivity in the back sheet. Architectural style has become fashionable for silicon wafer based products and two techniques have been used to add style to silicon-in-glass BIPV panels. As back ground, this design is not new and was first used from the mid 1990s when companies such as St-Gobain and Flatglas produced panels with partial or full filling of silicon wafers to provide a level of light transmission.
The most famous early example was a technology incubator building in Gelsenkirchen, which was reputed to keep the building warm even during the winter months. This problem of heat trapping and associated problems of differential thermal expansion causing connector failure and delamination of the EVA encapsulant reduced market uptake until more recently when architectural structuring (DGUs), improved encapsulants, and structured silicon wafers combined to create a fresh market acceptance. Companies such as Sunways have introduced, and effectively showcased at Intersolar, wafers with laser cut sections to reduce the light dappling and etch coloured wafers to create alternative colours to the unappealing black. Another approach shown was the incorporation of coloured EVA encapsulants.
After some years in which amorphous silicon has been in the background due to uncompetitive performance and lower durability, there were several companies such as Kaneka, Masdar, and Chinese second tier manufacturers, promoting single junction and multi-junction technologies with USPs of improved low light and shade performance, reduced negative temperature coefficient, plus structured warranties that are more commercially acceptable. Schott is still promoting its semitransparent ASI- Thru technology particularly for protected façade applications. Sanyo has improved its HIT hybrid crystalline/amorphous technology to the extent that it is now warranted in hot climates, though still with reduced durability compared to, say, European conditions.
CIG|S presence was less than anticipated, not just due to the disappearance of some players, but also due to the fact that some technological approaches are not as technically viable as promised. The leading companies such as Wurth offer a professional cost competitive product with similar USPs to amorphous silicon, but higher performance and supposedly better durability. Nevertheless, CIGS durability still depends on the quality of the sealing/encapsulation. In addition, CIGS continues to suffer from substantial drops in performance in low light conditions normally found in BIPV applications, particularly in Europe. When combined with the deep black 'colour' this makes CIGS unappealing as an architectural technology.
There was a virtual complete absence of 3rd Gen DSC and OPV companies, with only one entrant – Heliotek – the small organic molecule (inverted OLED) German start-up. The aesthetic features of the colours presented are undoubtedly attractive and the natural transparency is an added bonus. Technical personnel claim that 80C stability is now established when hermetically encapsulated in glass. Challenges are much more serious for flexible devices where the oxygen and moisture transmission through the typically PET substrates, render the devices useless in a month. The success of OPV in flexible applications will depend on the introduction of cheap 10-5 barrier layer technology and reducing the cost of ITO conductors by 75%.
Whereas, in Japan at PV Expo in February, several large corporations presented total home solutions this revolution is still in its infancy in Europe. The total home solution involves, sources of renewable energy, energy efficiency, storage – including EV storage, time of use appliances, and waste management. At that time, Toshiba presented its system in pink and unashamedly directed it at the female consumer – the person who selects for the home. Schuco was one of a few European companies now promoting this business sector.
In summary, 'ugly old silicon' still holds the technical position of pride, and attempts to improve aesthetics for building integration are addressing the change in market place from FIT driven solar farms to building distributed.
Whether these are sufficient to attract the consumer is another consideration!